title: Aging effects on the visually driven part of vergence movements.
abstract: OBJECTIVE
  To examine gain, speed, and temporal characteristics of initial and closed-loop components of vergence eye movements in young and elderly subjects.
  
  
  METHODS
  Vergence eye movements in 13 elderly and 10 young adults were examined. A table with light-emitting diodes was used to elicit vergence starting from near (convergence, 40-20 cm; divergence, 20-40 cm) or from far (convergence, 150-40 cm; divergence, 40-150 cm). Vergence eye movements were recorded with a video eye tracker or an infrared eye movement device.
  
  
  RESULTS
  There were no aging effects on the gain or peak velocity of vergence. Vergence duration was longer in elderly than in young adults, but only for the second, closed-loop components, driven by visual feedback. Elderly and young adults showed higher peak velocity and gain for convergence than for divergence.
  
  
  CONCLUSIONS
  This observation is discussed in the context of physiological evidence of a robust convergence, rather than a divergence, generator at the brain stem level. Such a specific effect of aging on the duration of the closed-loop component is attributed to the reduced capacity of cortical processing of visual binocular disparity; slowing of vergence would allow good final accuracy.
authors.affiliation: IRIS Physiopathologie de la vision et de la motricité binoculaire, Service d'Ophtalmologie-ORL-Stomatologie, Hôpital Européen Georges Pompidou, Paris, France. yangqing165@hotmail.fr
authors.forename: Qing
authors.initials: Q
authors.lastname: Yang
authors.forename: Thanh-Thuan
authors.initials: TT
authors.lastname: Le
authors.forename: Zoi
authors.initials: Z
authors.lastname: Kapoula
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003290:Convergence, Ocular / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D015348:Vision, Binocular / Q000502:physiology